Thread: Compressor Hating the Cold

Originally Posted by RustyArc

So three things occurred to me, it's a new machine, and hasn't cycled that much yet, so maybe it'll loosen up. Secondly, it typically gets left with the tank near full pressure, so when it cuts in, it's soon working against a pressurised tank. Thirdly, the oil is a straight SAE30. So I poured out the original oil, which probably wasn't a bad idea as it was clearly holding a lot of particles from the initial run-in of the new machine, and replaced it with a 10W-40 multigrade. Trying it this morning, after a -3 overnight and when it was probably about 6 degrees, it still tripped the overload, but promisingly, only took 4 cycles before it ran. Now I'm considering trying a 5W-40 to see if that offers any improvement.

Theres is your problem - use proper compressor oil and it will work properly.
I had the same problem with my compressor when I got it (in a used condition) and changed the oil to SAE30 - no good - it would not get past about 80 psi.
As soon as I put the right compressor oil in it ran fine.
The proper oil will also look after things much better than engine oil.

There are several grades of compressor oil and it also makes a difference which one you buy
H&F have it at a ridiculous price but I bought my oil from a Pilot Air branch and I think it cost 1/4 of the H&F price
http://www.pilotair.com.au/Products/...ressorOil.aspx

Originally Posted by BobL

As soon as I put the right compressor oil in it ran fine.
The proper oil will also look after things much better than engine oil.

I kinda wonder about that. I did a bit of reading about compressor oils before throwing in the 10W-40 engine oil. The salient question is, what actually *is* different between an engine and a compressor that would make an oil for the former inappropriate for the latter?

After seeing some of the overnite temps there recently, I'm surprised anythings working in the cold!!!!!

Been bad enough here in central Vic.

Originally Posted by jatt

After seeing some of the overnite temps there recently, I'm surprised anythings working in the cold!!!!!

One thing I've noticed is that a -7 morning *really* tests any dodgy plumbing you might have in a back shed. The most common failure is the copper pipe contracting to the point where it pulls out of compression fittings, particularly where a plastic olive has been used rather than copper. Our mains pressure sits at around 800kPa (almost 120psi). That means a *lot* of water when a fitting lets go. Best case scenario is the dodgy plumbing has also frozen, limiting the flow

Originally Posted by RustyArc

I kinda wonder about that. I did a bit of reading about compressor oils before throwing in the 10W-40 engine oil. The salient question is, what actually *is* different between an engine and a compressor that would make an oil for the former inappropriate for the latter?

I'm no mukanic, but I would say that as a compressor doesn't burn fuel, therefore requiring a non detergent oil, plus an internal combustion motor gets a lot hotter than a compressor, requiring a thicker oil, so when it thins down with heat, it still has its lubricating properties.
Kryn

Originally Posted by RustyArc

I kinda wonder about that. I did a bit of reading about compressor oils before throwing in the 10W-40 engine oil. The salient question is, what actually *is* different between an engine and a compressor that would make an oil for the former inappropriate for the latter?

After I had problems with my compressor I also did a bit of reading around this.

Most compressors do not have an oil pump and just rely on splash lubrication so the oils has to have a good splash characteristic (which is slightly different to viscosity) to lubricate the compressor..
OTOH internal combustion engines use a pump and they heat their oil much more and for long than a compressor does so they do not need oil with splash ability.
If the compressor cannot get sufficient oil the compressor motor may have to work so hard it may trip.
So to get your compressor running you could indeed use a lower viscosity oil since it will also splash better.

However, there is an additional reason not to do this and that is because the additives like detergents used in engine oil causes a compressor oil to foam and collect water and unlike an engine a compressor does not get hot enough for long enough to remove the water. The result is gunk build up around the valves and all round poorer lubrication.

Apparently it matters naught or little on old school, over engineered, low efficiency, compressors but as compressors are built lighter and closer to max efficiency the type of oils used does matter.

Originally Posted by RustyArc

One thing I've noticed is that a -7 morning *really* tests any dodgy plumbing you might have in a back shed. The most common failure is the copper pipe contracting to the point where it pulls out of compression fittings, particularly where a plastic olive has been used rather than copper. Our mains pressure sits at around 800kPa (almost 120psi). That means a *lot* of water when a fitting lets go. Best case scenario is the dodgy plumbing has also frozen, limiting the flow

It's your own fault for getting up that early in Canberra this time of year.
DAHIK

Originally Posted by KBs PensNmore

I'm no mukanic, but I would say that as a compressor doesn't burn fuel, therefore requiring a non detergent oil, plus an internal combustion motor gets a lot hotter than a compressor, requiring a thicker oil, so when it thins down with heat, it still has its lubricating properties.
Kryn

Yep that sums it up.

I must be one of the few people that have an ammeter and a temp gauge on their compressor. Well the temp gauge is not exactly on the compressor but it is in the actively vented compressor enclosure so I have a bit of an idea of the compressor temp.

When the compressor fires up (soft start using a VFD) it gets going and draws about 10-11A (3P 240V) then as the temp goes up the current draw goes down to around 8A until the pressure gets to around 80-90 PSI and then the temp and current both go up. Finally at around 135PSI the current draw is around 13A.

What I reckon is going on is at the start is the oil is cold and takes a while to get warm enough to fully lube the pump and then the current drops as it is under less load. Then as the pressure builds the motor has to work harder to keep pumping.

When I used engine oil the compressor motor would draw as much as 17A and while it would not trip out the 5HP VFD is was clearly struggling.
As soon as I changed to the right oil it worked as above.

I have always used SAE30 in my compressors, when I had a mower shop I had blokes coming in from the nearby factories all the time for me to fill their cans out of my 44 gal drum.
SAE30 is the oil that Briggs & Stratton engines use, all the smaller B&S engines use a splash oil system the same as small compressors.
Thanks for the reminder Rusty, I likely haven't changed my compressor oil for 10 yrs
I used to have a direct drive compressor and it had the same starting problems, first thing I noticed with it was the power lead was small enough to be suitable for a bed lamp so I replaced that with a grunty one, it helped a bit but it still would only start properly if it was plugged directly into a decent power point and I could never use it with an extension lead, belt drive comp's don't normally have this problem.
Do you use an extension lead for your compressor Rusty ? If so try it plugged directly into a power point and see how it starts.

shed

For what its worth my local oil supply company sold me 4 stroke mower oil as compressor oil. I haven't noticed a difference but I wouldn't have that many hours on it........ and it don't get that cold in my shed

Stuart

-7 I don't envy you. Frozen pipes, fittings letting go... doh!!!

Originally Posted by RustyArc

One thing I've noticed is that a -7 morning *really* tests any dodgy plumbing you might have in a back shed. The most common failure is the copper pipe contracting to the point where it pulls out of compression fittings, particularly where a plastic olive has been used rather than copper. Our mains pressure sits at around 800kPa (almost 120psi). That means a *lot* of water when a fitting lets go. Best case scenario is the dodgy plumbing has also frozen, limiting the flow

it wont happen if the plumbing is done correctly...the olive is meant to be a seal and a seal only!
the copper pipe should be croxed....a rolled protrusion carried out by a croxing tool, inside the end of the tube, which will prevent the tube from pulling out of the nut

Originally Posted by BobL

Yep that sums it up.

I must be one of the few people that have an ammeter and a temp gauge on their compressor. Well the temp gauge is not exactly on the compressor but it is in the actively vented compressor enclosure so I have a bit of an idea of the compressor temp.

you have gauges on everything...lol

my big compressor, Ingersoll rand 3HP is fitted to the door of the container, I use the compressor oil in it. never had any problems with it, even when it got really really cold a couple of weeks ago. I think it was down to 12d at 5am